b
(B) $\lambda \,\, = \,\,\frac{{\text{h}}}{{{\text{mv}}}}\,\,\, = \,\,\frac{{6.6 \times {{10}^{ - 34}} \times {{10}^7}}}{{25 \times 6.6 \times {{10}^4}\,cm/\sec }}erg\,\,\sec \,\,\,\, = \,1 \times \frac{{{{10}^{ - 38}}}}{{25}}$
$ = \,\,0.04 \times {10^{ - 38}} \times {10^7}\,\,\, = 0\,.04 \times {10^{ - 31}}\,cm\,\,\, = \,\,4 \times {10^{ - 33}}\,cm$